Yes, this is safe as both Moderna and Pfyzer have mRNA which act as the protectant against the virus. However, most individuals who received the Moderna shot voiced having side effect symptoms such as shortness of breath, chills and muscle aches which lasted for 1-2 days. These clients were advised to take any pain reliever as needed such as Tylenol or Advil. On the other hand, Pfyzer recepients did not voice any side effects, except for a sore muscle at the puncture site.

It's perfectly safe, but why would you do that? In 3-4 weeks, you should go back and have another Pfizer or Moderna shot. You'll be extra protected.

William Z. Cohen, M.D., FAAFP